The present invention relates to the field of optical films.
Microstructured transparent optical film has been used on glass, mirrors, vehicles, signs, ceilings and other surfaces for decorative purposes. One example is discussed in U.S. Pat. No. 5,840,407 to Futhey et al. in which a film used to simulate beveled glass is disclosed.
Commonly-assigned U.S. Pat. No. 3,908,056 to Anderson describes an optically decorative web that produces a real or virtual image that is other than that of an actual surface of the web. The Anderson optically decorative web is a strip of opaque or transparent polymeric material having a series of ridges and grooves on one side and a smooth surface on the other side. Examples of real or virtual images produced by the optically decorative web are metallic or transparent concave or convex surfaces, e.g., an arched ceiling which would be concave, giving the sensation of being in a room having a domed ceiling, a metallic strip on an automobile, molding on furniture, or the appearance of a semicylindrical glass or metallic bar extending across a glass panel.
Optically decorative films such as those taught by Anderson may include various structured lenticular Fresnel patterns. These thin Fresnel lensfilms can be designed to provide optical functionality similar to much thicker solid optical components. An incidental attribute of Fresnel lensfilm is that the lensfilm can appear macroscopically to have about the same amount of height or depth projection as the equivalent solid lens or prism surface. This characteristic can be utilized to produce thin decorative optically shaped film (OSF) that appears to be much thicker than its actual thickness. The surface of the OSF lensfilm can be a linear Fresnel prism or lens surface including an array of grooves having dimensions small enough to be not easily resolvable by the average unaided human eye. Typically, the depths of the majority of grooves in a Fresnel lensfilm design are held constant while the angle of one of the side walls (known as the facet angle) varies across the array, roughly matching at each location the angle of the solid prism or lens surface being simulated.
A Fresnel lensfilm often has structure only on one sidexe2x80x94the opposite side being smoothxe2x80x94but it can also be made with structure on both sides. In some applications, this increases the design flexibility and functionality of a single piece of lensfilm. Certain double-sided lensfilm designs have uniquely attractive appearances potentially giving them added value over single sided films in decorative OSF applications as well. However, the cost of producing film with structure on both surfaces is typically greater than the cost of producing single-sided film. This additional cost may be enough to preclude the use of double-sided film in many applications including decorative OSF applications where cost constraints can be severe.
The present invention provides a film having only one surface structured with two or more different, overlapping Fresnel patterns formed in the structured surface for use as thin, decorative optically shaped film.
The overlapping Fresnel patterns of the present invention cause an interruption in the various patterns. This interruption provides a complex optical pattern that has unique optical properties.
Although at least a portion of each Fresnel pattern in the devices/films of the present invention is interrupted, for the purposes of the present invention, a Fresnel pattern is a pattern of facets and risers that, but for the interruptions, would form a Fresnel lens or Fresnel prism.
Among the advantages provided by the present invention is the provision of a decorative optical film having structure on only one side that appears (to a viewer located on the same side of the film as the structured surface) very similar to films having a structure on both sides.
The optical effect provided by the optical film of the present invention may be combined with various articles for purposes of decoration and/or for offering protection to the article or protection to people, alerting them to the presence of the article, e.g., large plate glass windows or doors. For example, optical film may be applied to windows or mirrors to simulate beveled cuts or other decorative effects. The optical film may also be used on motor vehicles or bicycles as reflective warning tape. The film may also be applied to clothing and outerwear as reflective warning tape for improved safety. The present invention also has several uses as decoration, e.g., ribbons, streamers, wrapping paper, bows, costumes, eyewear, etc.
In one aspect, the present invention provides an optical film that includes a substrate including a first major surface; a first group of facets corresponding to a first Fresnel pattern formed in a first portion of the first major surface of the substrate; and a second group of facets corresponding to a second Fresnel pattern formed in a second portion of the first major surface of the substrate, wherein the first Fresnel pattern overlaps the second Fresnel pattern in a selected area of the first major surface of the substrate, and further wherein the first Fresnel pattern and the second Fresnel pattern interrupt each other in the selected area.
In another aspect, the present invention provides an optical film that includes a substrate including a first major surface; a first group of facets corresponding to a first Fresnel pattern including a linear Fresnel pattern that includes a first longitudinal axis formed in a first portion of the first major surface of the substrate; and a second group of facets corresponding to a second Fresnel pattern including a linear Fresnel pattern that includes a second longitudinal axis formed in a second portion of the first major surface, wherein the first Fresnel pattern overlaps the second Fresnel pattern in a selected area of the first major surface of the substrate, wherein the first longitudinal axis forms an angle with the second longitudinal axis, and further wherein the first Fresnel pattern and the second Fresnel pattern interrupt each other in the selected area.
In another aspect, the present invention provides an optical film that includes a substrate including a first major surface; a first group of facets corresponding to a first Fresnel pattern including a linear Fresnel pattern that includes a first longitudinal axis formed in a first portion of the first major surface of the substrate; and a second group of facets corresponding to a second Fresnel pattern including a linear Fresnel pattern that includes a second longitudinal axis formed in a second portion of the first major surface of the substrate, wherein the first Fresnel pattern overlaps the second Fresnel pattern in a selected area of the first major surface of the substrate, wherein the first longitudinal axis forms an angle with the second longitudinal axis, wherein the angle is greater than 0 degrees, and further wherein the first Fresnel pattern and the second Fresnel pattern interrupt each other in the selected area.
In another aspect, the present invention provides an optical assembly that includes a base substrate; an optical film attached to the base substrate that includes a film substrate including a first major surface; a first group of facets corresponding to a first Fresnel pattern formed in a first portion of the first major surface of the film substrate; and a second group of facets corresponding to a second Fresnel pattern formed in a second portion of the first major surface of the film substrate, wherein the first Fresnel pattern overlaps the second Fresnel pattern in a selected area of the first major surface of the film substrate, and further wherein the first Fresnel pattern and the second Fresnel pattern interrupt each other in the selected area.
These and other features and advantages of the present invention may be discussed below in connection with various illustrative embodiments of the invention.